Variable speed drives



Dec. 27, 1966 v A. H. BUTLER VARIABLE SPEED DRIVES Filed May 10, 1965Uited States Patent 3,294,369 VARIABLE SPEED DRlVES Alan Henry Butler,Urpington, England, assignor to The General Electric Qompany Limited,London, England Filed May 10, 1965, Ser. No. 455,054 Claims priority,application Great Britain, May 8, 1964, 19,272/64 6 Claims. (Cl.254-172) This invention relates to a rotary output device, that is tosay a motor unit or a pump unit of the kind having one member whichrotates with respect to another when the device is operating to providethe required output, and relates also to arrangements incorporating suchdevices.

In the case of a pump the output is provided by the flow of fluidthrough the pump and in the case of a motor the output is provided bythe power developed by the motor.

According to one aspect of the invention in a rotary output device ofthe kind having a first member which is rotatable with respect to asecond member when the device is operating to provide a required output,the second member is itself mounted for rotation about an axiscoincident with the axis of the first member, and means'are provided forcontrolling the rotation of the second member so as to vary the outputof the device.

Where the device is provided by a constant output speed motor, theinvention provides a way of varying the effective output speed of themotor, and in the case of a pump having a first member designed to berotated at a constant speed in use of the pump, the invention provides away of controlling the rate of flow of fluid through the pump.

One particular application of the invention is in a winch arrangement ofthe kind which is adapted to be connected via a winch drum and cable toa load member which may fluctuate from time to time, said wincharrangement being controlled by a hydraulic fluid circuit.

According, therefore, to another aspect of the invention, in such awinch arrangement, the hydraulic fluid circuit includes a drive assemblycomprising a hydraulic motor unit and a hydraulic pump unit, each unithaving a pair of relatively rotatable members, one member of one unitbeing connected to one member of the other unit, and the other membersof the units being connected between a fixed support and the winch drumin such a manner that in operation of the hydraulic fluid circuit, themotor unit provides a substantially constant torque to said drum, andany power in excess of that required to provide said substantiallyconstant torque to the drum is used to drive the hydraulic pump, theunit which is connected to the winch drum providing the rotary outputdevice in accordance with the first aspect of the invention.

It will be appreciated that with the hydraulic circuit described abovethe power provided by the motor is shared between the winch drum and thepump; however when the winch drum is stationary or rotating at aconstant low speed due to the load member being steady, the constanttorque to the drum is provided merely by the reaction between the pairof relatively rotatable members of the motor unit, and thereforesubstantially all of the power of the motor unit will be used to drivethe pump. If now the load member fluctuates in a way which would tend toproduce a slackening of the cable, and causes the winch drum to haul incable, the power provided by the motor unit will be divided between thewinch drum and pump unit, in a ratio which is dependent upon the amountof power required by the winch drum to correct for the fluctuation inthe load member. Thus the output of the pump will be decreased.Similarly if the load member fluctuates in such a way that the cableacts on the winch drum to cause it to pay out cable, the drum rotationpro- 3,294,369 Patented Dec. 27, 1966 ice vides extra power over thatprovided by the motor unit and thus this extra power adds to the motorunit power to increase the output of the pump unit.

In one arrangement of motor and pump units, the hydraulic motor unit mayhave its casing and output shaft, constituting the pair of relativelyrotatable mem bers, connected to the winch drum and the input shaft of ahydraulic pump unit respectively, the pump casing being fixed.

In another arrangement, the hydraulic pump unit may have its input shaftand casing connected to the winch drum and the output shaft of thehydraulic motor unit respectively, the motor casing being fixed.

The hydraulic circuit may include a plurality of drive assemblies eachcomprising a hydraulic motor having a hydraulic pump associatedtherewith and each being similarly coupled to the winch drum, eitherdirectly or through suitable gearing.

The hydraulic fluid circuit may also be provided with a high-pressureand a low-pressure side.

It will be appreciated that suitable valves would also be provided inthe hydraulic fluid circuit to ensure its correct working.

A further pump unit may be provided between the low-pressure andhigh-pressure sides of the circuit, the further pump being operable tomake up efliciency losses in the circuit.

Each hydraulic motor and pump arrangement may be connected togetherthrough gearing or the motor and pump may be of diiferent sizes toreduce efficiency losses in the circuit.

In order that the invention may be readily understood, one wincharrangement embodying the invention will now be described, by way ofexample, with reference to the accompanying drawing, which is aschematic diagram of the arrangement.

Referring to the drawing, the winch arrangement comprises a rotatablewinch drum 1 which rigidly carries a spur gear 2 at one of its ends. Aplurality of drive assemblies, each comprising a hydraulic motor 3connected to a pump 8, are mounted on a suitable support structure (notshown) and are disposed at equal intervals around the circumference ofthe spur gear 2 (only two assemblies being shown in the drawing for thesake of clarity). The motor casing 4 of each motor 3 rigidly carries aspur gear 5 which meshes with the spur gear 2. The output shaft 6 ofeach motor 3 is directly coupled to the input shaft 7 of the pump 8 andthe casing 9 of each pump is fixed to a suitable support structure (notshown). The hydraulic motors 3 and pumps 8 form part of a hydraulicfluid circuit, generally denoted 11 in which the high pressure lineshave been shown thicker than the low pressure lines.

Referring now to the hydraulic circuit 11, a low pressure accumulator 12feeds the pump 8 from a common supply line 13 via non-return valves 14.The pumps 8, when operating, are arranged to feed fluid at high pressureto the high-pressure side of the circuit which includes a high pressureaccumulator 15, via non-return valves 16 and pressure relief valves 17,and the high-pressure side of the circuit is arranged to feed the motors3 through a high pressure line 18 via non-return valves 19. A flowcontrol valve 21 is provided in the line 18 between the accumulator 15and each motor 3 to ensure a constant fluid input to the motors so thatthe motors provide a constant output torque and constant speed, andhence a constant power to the spur gear 2 of the winch drum 1.

The spent pressure fluid from the motors 3 is fed back to the lowpressure supply via lines 22 for recirculation through the pumps 8, andany leakage of pressure fluid from the motors and pumps is fed via lines23 and 24 to a reservoir 25 where it is fed back to the low pressuresupply via a pump 26 and a non-return valve 27. A further pump 28 isprovided between the low pressure supply line 13 and the high pressuresupply line 18 which is operable to make up for any efliciency losses inthe high pressure circuit.

In operation of the winch arrangement when the load member is steady,the torque applied to the winch drum 1 by its cable is balanced out bythe torque applied to the drum via the casings 4 of the hydraulic motors3 via the spur gears 5 and 2. Thus the drum 1 and hence the motorcasings 4 may be rotating at a low constant speed or may be at zerorevolutions and therefore substantially no power is being used by thedrum, but instead is being used to drive the pumps 8 in a constantdirection at a substantially constant speed via the shafts 6 and 7 ofthe motors 3 and pumps 8 respectively.

If now the load member fluctuates and subjects the winch drum to anincreased load, the drum accelerates in one rotational direction tounwind the cable, since the torque then applied to the winch drum by thecable exceeds the constant torque applied via the motors 3. The motorcasings 4 will therefore be rotated in one direction by the winch drum.In this situation the direction of rotation of the shafts 6 of themotors 3 relatively to their motor casings 4 is the same as thedirection of rotation of the motor casings 4 and therefore the speed ofthe pumps 8 is effectively increased. Thus additional power is suppliedto the motors 3, this regenerative power being absorbed by the pumps 8which supply an increased variable amount of high pressure fluid to thehigh-pressure side of the circuit depending on the speed of rotation ofthe motor casings 4, and the arrangement is such that the resistingtorque of the pumps is constant with the result that a constant torqueis applied through the motor casings 4 to the winch drum 1. Similarly,if the load member fluctuates to subject the winch drum 1 to a decreasein load, the drum accelerates in its other rotational direction to takeup the slack in the cable, since the constant torque applied to the drumthen exceeds that applied to the load member. The direction of rotationof the mot-or casings 4 is then in opposition to the direction ofrotation of their shafts 6 and therefore the speed of the pumps 8 iseffectively decreased. Thus the power of the motors 3 is being dividedbetween the winch drum 1 and pumps 8 up to the limiting case where thetotal power of the motors 3 is being used to rotate the winch drum 1.This of course would mean that the pumps 8 would be rendered inoperativeand the whole of the power was being absorbed by the drum.

It will be appreciated that the motor and pump arrangements could bemounted within the winch drum if desired and that the shafts 6 and 7 ofthe motors and pumps could be coupled together through gearing or othersuitable means to provide a ratio between the motors and pumps or themotor and pump units could be of different capacities to assist thefurther pump 28 in making up for efficiency losses in the hydrauliccircuit, in which case the capacity of the further pump 28 could bedecreased. Also the positions of the hydraulic motor and pump unitscould be changed so that the pump unit was connected between the motorand the winch drum. With the pump unit between the motor and winch drum,if the pump casing was connected to the output from the motor then understeady conditions of the load member the input shaft of the pumpconnected to the winch drum would be stationary and the pump casingwould be rotating at the speed of the motor. If now the load memberfluctuated the winch drum would cause the input shaft of the pump torotate in one direction or the other but would not alfect the speed ofthe pump casing. Thus, the only inentia to overcome in such anarrangement would be that of the pump input shaft.

I claim:

1. A winch arrangement comprising a fixed support, a winch drum mountedon the fixed support, a support cable wound on said winch drum andconnectable to a load member which may fluctuate from time to time, anda hydraulic fluid circuit for controlling the winch drum, said hydraulicfluid circuit including at least one drive assembly which comprises ahydraulic motor unit having a pair of relatively rotatable members and ahydraulic pump unit also having a pair of relatively rotatable members,one member of one unit being connected to one member of the other unitand the other members of the units being connected between the fixedsupport and the winch drum so that in operation of the hydraulic fluidcircuit, the motor unit provides a substantially constant torque to saiddrum, and any power in excess of that required to provide saidsubstantially constant torque to the drum is used to drive the hydraulicpump.

2. A winch arrangement as claimed in claim 1, in which the hydraulicmotor unit comprises a casing and an output shaft, and the hydraulicpump unit comprises a casing and an input shaft, said casing and shaftin each case constituting the pair of relatively rotatable members, andthe casing and output shaft of the hydraulic motor unit are connected tothe winch drum and input shaft of the hydraulic pump unit, respectively,the pump casing being fixed on said fixed support.

3. A winch arrangement as claimed in claim 1, in

which the hydraulic motor unit comprises a casing and an output shaftand the pump unit comprises a casing and input shaft, said casing andshaft in each case constituting the pair of relatively rotatablemembers, and the hydraulic pump unit has its input shaft and easingconnected to the winch drum and the output shaft of the hydraulic motorunit, respectively, the motor casing being fixed.

4. A winch arrangement as claimed in claim 1, in which the hydraulicfluid circuit includes a plurality of drive assemblies each comprising ahydraulic motor having a hydraulic pump associated therewith and eachbeing similarly coupled to the winch drum, either directly or throughsuitable gearing.

5. A winch arrangement as claimed in claim 4, in which the hydraulicfluid circuit is provided with a highpressure and a low-pressure side.

6. A winch arrangement as claimed in claim 4, in which a further pumpunit is provided between the lowpressure and high-pressure sides of thecircuit, the further pump being operable to make up efficiency losses inthe circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,763,467 9/1956Doolittle 254172 EVON C. BLUNK, Primary Exdminer. H. C. HORNSBY,Assistant Examiner.

1. A WINCH ARRANGEMENT COMPRISING A FIXED SUPPORT, A WINCH DRUM MOUNTEDON THE FIXED SUPPORT, A SUPPORT CABLE WOUND ON SAID WINCH DRUM ANDCONNECTABLE TO A LOAD MEMBER WHICH MAY FLUCTATE FROM TIME TO TIME, AND AHYDRAULIC FLUID CIRCUIT FOR CONTROLLING THE WINCH DRUM, SAID HYDRAULICFLUID CIRCUIT INCLUDING AT LEAST ONE DRIVE ASSEMBLY WHICH COMPRISES AHYDRAULIC MOTOR UNIT HAVING A PAIR OF RELATIVELY ROTATABLE MEMBERS AND AHYDRAULIC PUMP UNIT ALSO HAVING A PAIR OF RELATIVELY ROTATABLE MEMBERS,ONE MEMBER OF ONE UNIT BEING CONNECTED TO ONE MEMBER OF THE OTHER UNITAND THE OTHER MEMBERS OF THE UNITS BEING CONNECTED BETWEEN THE FIXEDSUPPORT AND THE WINCH DRUM SO THAT IN OPERATION OF THE HYDRAULIC FLUIDCIRCUIT, THE MOTOR UNIT PROVIDES A SUBSTANTIALLY CONSTANT TORQUE TO SAIDDRUM, AND ANY POWER IN EXCESS OF THAT REQUIRED TO PROVIDE SAIDSUBSTANTIALLY CONSTANT TORQUE TO THE DRUM IS USED TO DRIVE THE HYDRAULICPUMP.